Mozilla, Google take different approaches to ad tracking opt-out

Google has announced the availability of an add-on that will allow users to …

Google announced today the availability of a browser add-on for Chrome that will make it easier for users to opt out of the behavioral tracking that Internet advertising companies use to improve ad targeting. The add-on relies on a standardized cookie-based opt-out system that is supported by a growing number of companies, including the 15 largest advertising networks.

Mozilla has also announced its own effort to facilitate user opt-out of Internet tracking. Dissatisfied with the technical inelegance of Google's approach, Mozilla has proposed a simpler and more robust method that would involve using browser headers rather than cookies. Although it's a better long-term solution, Mozilla will have to get buy-in from the advertising companies before it will actually work.

Behavioral tracking has generated considerable concern among privacy advocates. The advertising industry has responded by taking voluntary steps to support consumer opt-out options. The Network Advertising Initiative (NAI), which represents a coalition of major Internet advertising companies, already provides a simple Web-based tool that will allow users to configure tracking opt-out cookies. The NAI's tool is a good start, but its key weakness is that the user's opt-out settings don't remain intact if the user erases her cookies.

Google's new add-on will simplify the opt-out process and ensure that it always remains intact, even if the user's cookies get eaten. The add-on ties into the browser's internal cookie APIs in order to make sure that the proper opt-out setting is configured for each advertising network. To accomplish this, it bundles a simple JSON-based registry of the major advertising network domains and the value that has to be set in the cookie for each one in order to opt out of tracking.

Google's approach is effective and pragmatic because it simply wraps the existing cookie-based opt-out mechanisms that are offered by the advertising companies. The manner in which it attempts to intercept and rewrite cookies, however, poses some minor challenges and is arguably a suboptimal technical solution.

On a tangentially related note, I was somewhat amused by the level of angst exhibited by the comments and documentation in the add-on source code. The Google developer who worked on the project contends that Chrome's add-on APIs for cookies are "annoyingly deficient" and complains that one of the workarounds he had to use was an "ugly ugly ugly" hack.

Mozilla's privacy officer, Alex Fowler, recently posted a blog entry with a proposal for an alternate system, one that will rely on HTTP headers rather than cookies. Applications could simply append a "Do Not Track" header that would indicate to the service that the user doesn't want to be tracked.

The header approach has the advantage of being a simpler and more generic solution that is easier to implement on the client side. It would also obviate the need to manage inconsistent values across dozens of cookies. Mozilla says that the header would be tied to a browser preference that can be toggled by the user. The Do Not Track mode would not be enabled by default, however.

Mozilla's solution makes sense in the long term, but it's still at the proposal stage. There is no real implementation yet and the convention will need to be adopted by advertisers before it would become effective. Mozilla says that it's still also looking seriously at pragmatic interim solutions (which will probably be similar to Google's add-on) during the ongoing effort to formulate and build consensus around the header-based approach.

It's important to note that neither Google's add-on or Mozilla's proposed header will actually block tracking. Both solutions rely on the advertising industry to respect the user's preference regarding tracking. The major players have all demonstrated a willingness to participate in self-regulation efforts, however, which suggests that they will likely be receptive to collaborating with the browser vendors on proposed solutions.